Introduction to Layered Topic Maps - Revision history

Akivela: /* Ambiguity of operations */

2013-12-03T16:43:33Z

‎Ambiguity of operations

Akivela at 21:03, 10 February 2010

2010-02-10T21:03:05Z

Akivela: Introduction to Layered Topic Map moved to Introduction to Layered Topic Maps

2008-06-30T08:11:45Z

Introduction to Layered Topic Map moved to Introduction to Layered Topic Maps

Akivela: Layered Topic Map moved to Introduction to Layered Topic Map

2008-06-30T08:03:22Z

Layered Topic Map moved to Introduction to Layered Topic Map

Olli: /* Layered topic maps in Wandora */

2008-04-30T07:25:51Z

‎Layered topic maps in Wandora

Olli: /* Layered topic maps in Wandora */

2008-04-30T06:30:44Z

‎Layered topic maps in Wandora

Akivela: /* Problems with merging */

2008-04-28T08:19:57Z

‎Problems with merging

Olli at 09:41, 21 September 2006

2006-09-21T09:41:44Z

Olli at 09:41, 21 September 2006

2006-09-21T09:41:29Z

Olli: /* Layered topic maps in Wandora */

2006-09-21T09:23:06Z

‎Layered topic maps in Wandora

← Older revision		Revision as of 16:43, 3 December 2013
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	One might think that performing the operation for all possible topics would be more intuitive. However, in many cases this would result in loss of information. For example when editing base name or adding a subject identifier, performing the operation for all topics would cause all the topics to have same base name or subject identifier and thus the topics would be merged which probably is not what was intended.		One might think that performing the operation for all possible topics would be more intuitive. However, in many cases this would result in loss of information. For example when editing base name or adding a subject identifier, performing the operation for all topics would cause all the topics to have same base name or subject identifier and thus the topics would be merged which probably is not what was intended.
		+
		+	== See also ==
		+
		+	* [[Creating new layers]]
		+	* [[Layered topic map]]
		+	* [[Layer order and arranging layers]]
		+	* [[Topic's layer distribution]]

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 === Adapter layers ===
-The merging rules can be used make an adapter topic map that is used to combine two different topic maps. This is needed when two or more topic maps that have overlaping information but use different vocabulary and subject identifiers need to be merged. Because of the different vocabulary and subject identifiers, topics that represent same conepts would not be merged. An adapter topic map in a sense translates the indentifiers back and forth. This is done by creating topics that contain identifiers from both topic maps. This causes topics from both topic maps to merge with topics in the adapter topic map and thus the topics in the two original topic maps are merged together.
+The merging rules can be used make an adapter topic map that is used to combine two different topic maps. This is needed when two or more topic maps that have overlapping information but use different vocabulary and subject identifiers need to be merged. Because of the different vocabulary and subject identifiers, topics that represent same concepts would not be merged. An adapter topic map in a sense translates the identifiers back and forth. This is done by creating topics that contain identifiers from both topic maps. This causes topics from both topic maps to merge with topics in the adapter topic map and thus the topics in the two original topic maps are merged together.
 [[Image: layered_adapter_example.png]]
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 == Ambiguity of operations ==
-The visible topic may be a combination of several topics of the selected layer. This often results in some operations being ambiguous. For example if we are changing a base name, we would normally choose the version of the visible topic in the visible layer, or if such does not exist duplicate it implicitely, but there may be several of such topics. Currently these are resolved by simply using one of the topics.
+The visible topic may be a combination of several topics of the selected layer. This often results in some operations being ambiguous. For example if we are changing a base name, we would normally choose the version of the visible topic in the visible layer, or if such does not exist duplicate it implicitly, but there may be several of such topics. Currently these are resolved by simply using one of the topics.
 One might think that performing the operation for all possible topics would be more intuitive. However, in many cases this would result in loss of information. For example when editing base name or adding a subject identifier, performing the operation for all topics would cause all the topics to have same base name or subject identifier and thus the topics would be merged which probably is not what was intended.

@@ Line 19: / Line 19: @@
 Each layer contains one topic map. You can use different topic map implementations in each layer. For example you can use a database stored topic map in one layer and memory implementation in another. It is also possible to use a layered topic map in a layer which makes it possible to organize layers in several layer groups. This will result in a tree structure where layered topic maps resemble folders in a file system.
-At all times, one of the layers is selected. All edit operations are done in the topic map of this selected layer. This may cause implicit duplication of topics when the visible topic is not in the selected layer. This is discussed in more detail below. If you use layered topic maps in layers, choice of selected layer is slightly more complicated. All edit operations are always done in a leaf layer, that is a layer that is not a layered topic map. Hence if you select a layered topic map layer, all edit operations will actually be done in some child layer of the selected layer. This layer will be the last selected layer under the layered topic map and it is highlighted in the GUI with a slightly lighter colour than the selected layer.
+At all times, one of the layers is selected. All edit operations in the topic map are done in this selected layer. This may cause implicit duplication of topics when the visible topic is not in the selected layer. This is discussed in more detail below. If you use layered topic maps in layers, choice of selected layer is slightly more complicated. All edit operations are always done in a leaf layer, that is a layer that is not a layered topic map. Hence if you select a layered topic map layer, all edit operations will actually be done in some child layer of the selected layer. This layer will be the last selected layer under the layered topic map and it is highlighted in the GUI with a slightly lighter colour than the selected layer.
 Note that the layers in Wandora resemble the layers paradigm used in many image manipulation programs. Just like in Wandora, these programs allow user to switch layer visibility and all edit operations are done in the layer user has selected. Also topmost layers overwrite information from bottom layers by drawing over them.

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 The order of layers is used to decide which piece of information is visible when there are different values for some properties of topic. In the reduced topic maps that Wandora uses, topics can have only one base name, only one subject locator and only one occurrence for each scope. If two topics that will be merged have different values for one of these properties, we have to decide which of the possible values actually is used in the merged topic map. Value from the topmost layer is used, if there are several different values in topmost layer, one of them is chosen arbitrarily. Note that we wouldn't need to do this if Wandora used complete standard topic maps, because they may have several base names, subject locators and occurrences. We could simply have them all in the merged topic.
-At all times, one of the layers is selected. All edit operations are done in the topic map of this selected layer. This may cause implicit duplication of topics when the visible topic is not in the selected layer. This is discussed in more detail below.
+Each layer contains one topic map. You can use different topic map implementations in each layer. For example you can use a database stored topic map in one layer and memory implementation in another. It is also possible to use a layered topic map in a layer which makes it possible to organize layers in several layer groups. This will result in a tree structure where layered topic maps resemble folders in a file system.
 Note that the layers in Wandora resemble the layers paradigm used in many image manipulation programs. Just like in Wandora, these programs allow user to switch layer visibility and all edit operations are done in the layer user has selected. Also topmost layers overwrite information from bottom layers by drawing over them.

@@ Line 3: / Line 3: @@
 == Problems with merging ==
-Suppose we have two topic maps which both describe artists. They have been created from different points of view however, one deals mostly with biographical information about artists and the other has details about works the artists have created. They overlap mostly, but not completely, meaning that most of the artists in one topic map are present also in the other topic map but in some cases there isn't biographical information about an artist that has pictures in the other topic map or vica versa. Suppose also that both topic maps contain date of birth and date of death of most artists. In some cases these might have not been known and thus are not in the topic map.
+Suppose we have two topic maps which both describe artists. They have been created from different points of view. One deals mostly with biographical information about artists and the other has details about works the artists have created. They overlap mostly, but not completely, meaning that most of the artists in one topic map are present also in the other topic map but in some cases there isn't biographical information about an artist that has pictures in the other topic map or vica versa. Suppose also that both topic maps contain date of birth and date of death of most artists. In some cases these might have not been known and thus are not in the topic map.
 We can merge these two topic maps to form a topic map with all the combined information. After merge it is however impossible to solve where some piece of information originated from. Any artist might have been in either or both of the topic maps just like a date of birth might have been in either or both. Suppose we find a mistake in the date of birth of some artist and want to fix it. There is no way to know which one of the original topic maps had the wrong date without inspecting the original topic maps. With associations and a greater number of merged topic maps things become even more complex.

← Older revision		Revision as of 09:41, 21 September 2006
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−	Merging of topics is a very powerfull feature of [[~~topic maps~~]]. However it also introduces some problems. Wandora uses a layered topic map paradigm to counter some of these problems and also to introduce new ways of using topic maps. Unfortunately the layer paradigm also introduces some new problems which are also discussed here.	+	Merging of topics is a very powerfull feature of [[Topic Maps]]. However it also introduces some problems. Wandora uses a layered topic map paradigm to counter some of these problems and also to introduce new ways of using topic maps. Unfortunately the layer paradigm also introduces some new problems which are also discussed here.

	== Problems with merging ==		== Problems with merging ==